The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physical conditions. For example, lactate, cholesterol, and bilirubin should be monitored in certain individuals. In particular, determining glucose in body fluids is important to individuals with diabetes who must frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered. In one type of testing system, test sensors are used to test a fluid such as a sample of blood.
Many individuals test their blood glucose several times per day. Thus, the individuals often must carry with them a meter for determining the glucose concentration of their blood. The individuals may also carry with them other analyte-testing instruments, including test sensors, a lancet, disposable lancets, a syringe, insulin, oral medication, tissues, or the like. Thus, the individuals are able to perform testing of their blood glucose at different locations including their homes, places of employment (e.g., office buildings or work sites), places of recreation, or the like. Carrying the meter and/or other analyte-testing instruments to these various locations may be inconvenient.
Blood glucose meters can be powered using various types of powering configurations such as batteries or adapters that can be plugged into a standard outlet. The use of batteries allows the device to be portable and mobile without using a power outlet. Batteries available for use in blood glucose meters include both disposal batteries and rechargeable batteries. The use of a rechargeable battery for a blood glucose meter requires the battery to have a charge for the meter to function. Sometimes when a battery is discharged, a critical situation may arise that requires an emergency blood glucose test.
Measurement of blood glucose concentration is typically based on a chemical reaction between blood glucose and a reagent. The chemical reaction and the resulting blood glucose reading as determined by a blood glucose meter is temperature sensitive. Therefore, a temperature sensor is typically placed inside a blood glucose meter. The calculation for blood glucose concentration in such meters typically assumes that the temperature of the reagent is the same as the temperature reading from the sensor placed inside the meter. However, if the actual temperature of the reagent and the meter are different, the calculated blood glucose concentration will not be accurate. An increase in temperature or the presence of a heat source within a blood glucose meter will generally result in an erroneous measurement of blood glucose.
Power management in a battery-powered blood glucose meter can include using a battery fuel gauge to monitor the state of battery charge. A battery fuel gauge typically monitors, on a continual basis, the current flowing in both directions through the battery of the meter. However, such continuous monitoring also requires the battery fuel gauge to operate constantly, which results in increased power consumption, even when the battery-powered blood glucose meter is in a sleep mode. The increased power consumption requires a larger battery size and increases battery cost, particularly for portable devices.
It would be desirable to have a battery-powered meter that can be rapid charged without a significant temperature rise. It would also be desirable to manage the power consumption of a battery-powered meter to minimize power consumption during periods of non-use while maintaining an accurate assessment of the state of battery charge.